For example, in a related-art vehicle drive system of Patent Literature 1 described below, there has been proposed a system in which a boost converter is arranged between a battery and a motor to cover a drive region with use of a small-size motor without increasing the number of series-connected cells of a battery.
Further, for example, in Patent Literature 2 described below, there has been proposed a control method of switching a series connection and a parallel connection of a plurality of batteries to prevent degradation in chargeability of the batteries during low-speed traveling and degradation of the batteries due to a large charge current during high-speed traveling.